Abstract: OBJECTIVE: To study the expression changes of Arp2，Arp3 and cofilin genes of lymphocytic microfilament in thymus gland induced by different doses of γ-rays in BALB/c mice. METHODS：40 BALB/c mice were divided into five groups. Four groups were separately exposed toγ-rays with 0.02，0.1，1 and 6 Gy in whole body. One group was control. Every group had 8 mice. After 3 hours induced byγ-rays，the mice were given cervical dislocation，chests and thymuses were collected. Thymus cells were flowed out by PBS immited. mRNA and proteins of Arp2，Arp3 and cofilin genes were extracted from thymus cells. Their mRNA expressions proteins were detected by fluorescent quantitation PCR. The Arp2，Arp3 and cofilin proteins were measured by western-blot. RESULTS： Compared with control， mRNA expressions of Arp2 gene induced by γ-rays with different doses were not statistically significant，but Arp2 protein expressions induced byγ-rays with 1Gy were upward (H=2.33， P<0.05)；mRNA expressions of Arp3 gene induced by γ-rays with 1 Gy were downward (t =-12.77，P<0.01)，mRNA expression of Arp3 gene induced by 6 Gyγ-rays were upward (t = 3.39，P<0.05)，differences of Arp3 protein expressions induced by γ-rays with different doses were not statistically significant；mRNA expressions of cofilin gene of groups induced seperately byγ-rays with 0.02，0.1 and 1 Gy were upward (t =6.38-9.41，P<0.01)，while differences of cofilin protein expressions induced by γ-rays with different doses were not statistically significant. CONCLUSION：Afterγ-rays induced with different doses，the expressions changes of Arp2，Arp3 and cofilin genes took place in thymus gland of BALB/c mice. Characteristics of the their changes were associated with doses of γ-rays. These results provided experimental evidences for the mechanism of changes of lymphocyteic microfilament meshwork induced by γ-rays.

Key words: γ-rays, lymphocyte, thymus gland, Arp2, Arp3, cofilin